Nearly 8 years after Oklahoma City took part in an EPA program called Greening America’s Capitals, it is slowly moving ahead with one of the projects—the construction rain gardens to control stormwater.
The project was mentioned briefly in a recent city water publication which focused on the city plan to build a network of rain gardens to capture stormwater and reduce the amount in city streets, in creeks and underground storm drains.
“To this end, the City plans to build rain gardens near NW 29TH Street and Walker Avenue, as one of the voter-approved Better Streets, Safer City sales tax extension projects,” stated the publication.
The publication did not offer an explanation of a rain garden, but the EPA described them as depressed areas in the landscape to collect rainwater from a roof, driveway or street and allow it to soak into the ground. Planted with grasses and flowering perennials, rain gardens can be a cost effective and beautiful way to reduce runoff from your property. Rain gardens can also help filter out pollutants in runoff and provide food and shelter for butterflies, song birds and other wildlife.
T.O. Bowman, a Program Planner in the city’s Office of Sustainability in the Planning Department explained, “This is the last remaining vestige of the Greening America’s Communities report from 2017-18 that included public meetings and technical assistance from the EPA. There were recommendations about connectivity, walkability, and storm water/flooding issues in the five project sites, one of which was Walker Ave.”
It was also part of the 2023 Urban Heat Island Mapping Campaign covering about 350 square miles in the city. That’s when Oklahoma City participated in the nationwide effort to measure temperatures and locate the Urban Heat Islands in the city which included heat-absorbing surfaces, like buildings, streets and parking lots in areas with less shade, vegetation, and trees. This is known as the Urban Heat Island (UHI) effect. Metal and glass buildings reflect the sun’s energy and concrete, asphalt, stone and bricks absorb and radiate that energy. These surfaces slowly release the heat absorbed during the day, making nights and mornings hotter. Urban areas are about 7 degrees Fahrenheit hotter on average than more vegetated, outlying areas, according to the EPA. In Oklahoma City, people feel the UHI effect downtown, in industrial areas, and in neighborhoods that don’t have significant tree cover. People also feel the effects of those “hot spots” in densely developed housing additions where newly planted trees are still maturing.
Urban Heat In OKC
The National Oceanic and Atmospheric Administration (NOAA), the Oklahoma City Community Foundation, Oklahoma Department of Environmental Quality, and the Association of Central Oklahoma Governments all provided funding and consultant CAPA Strategies, loaned sensors for the study and performed technical assistance, data analysis and produced summary reports. OS staff and dozens of partner organizations recruited more than 250 volunteers who placed temperature and air quality sensors on their vehicles and drove in specific routes around the city in the morning, midday, and late afternoon shifts. The Oklahoma Department of Agriculture, Food and Forestry supported the campaign by taking infrared photos using a drone to illustrate the different temperatures of various materials.
The City’s findings, including an online map and several reports, are provided at www.okc.gov/extremeheat. The data showed warmer surface temperatures in the morning and a 15-degree difference between the hottest and coolest parts of OKC that day.
Urban Heat Connections to Storm Water Quality
The UHI effect can also increase storm water runoff temperatures and negatively affect life in nearby lakes, creeks and streams. This is known as thermal pollution. During a storm, the air temperature heats up rain drops as they fall. As rain hits pavement in an urban area and runs off toward a storm drain, the stormwater picks up additional heat. When creeks and streams drain into ponds or lakes, the warmer water creates conditions which favor harmful algae growth, potentially leading to excessive algal blooms and reduced oxygen concentrations in the water.
To reduce surface temperatures, some cities look to low-impact development (LID), which is infrastructure built to mimic natural systems by slowing down storm water runoff, spreading it out, or holding it temporarily. LID features like rain gardens and bioswales may look like regular flower beds but have functional drainage features below ground. Scissortail Park features circular bioswales with native or adapted plants around the edges and center, filtering pollutants, lowering temperatures and slowly absorbing the water into the soil.
Building a network of rain gardens can capture stormwater and reduce the amount in city streets, in creeks and underground storm drains. To this end, the City plans to build rain gardens near NW 29TH Street and Walker Avenue, as one of the voter-approved Better Streets, Safer City sales tax extension projects.
Developing guidance, piloting LID projects, and studying the urban heat island effect are all recommendations from the City’s sustainability plan, adaptokc. The City published a progress report covering the first five years of implementing the plan in March.
Bowman explained to OK Energy Today the city’s Public Works Department played a central role in the development of the application for, and meetings associated with the technical assistance that produced the report and led to the conversations to include any amount of “low-impact development” features in the streetscape project.
“Public Works was kind enough to work with us and include these as a “pilot project” of sorts, and the intent is to reduce sediment and other pollutants flowing downstream toward Edgemere Park and beyond. The rain gardens are engineered with underdrains connecting to the primary storm water system. They allow some storm water to enter from the street where it can be temporarily held and slowly percolate into the system via overflow drains from what I gathered from the most recent drawings.”
What’s the cost of the rain gardens? The city could not provide an answer. Nor was any timeline on construction available from the city.
